Mobile computer devices, e.g., smartphones, tablet computers and mobile media players, share a growing popularity among users in recent years. Especially since the introduction of the “iPhone”® of Apple Inc., Cupertino, USA, the share of smartphones in the total market of mobile telephone has steadily increased. With the “iPad”, a tablet computer, a new device class of mobile computer devices was successfully established. In addition, the computing power of mobile media players, e.g., the “iPod”, which are able to play audio and video data, is not insignificant.
A smartphone is a mobile telephone which besides telephone functionality provides for additional functionality like calendar, email and an internet browser. Therefore, the type of connection into the mobile telephone network is not restricted to pure speech connections as with conventional mobile telephones. Rather, a additional data connection is also provided for offering the user services like email, internet browser and social media like Twitter® and Facebook®.
A tablet computer is a mobile computer, which often comprises a touch sensitive display, instead of a keyboard, for enabling operation of the device. Compared to laptop computers, a tablet computer is most often lighter and smaller, such that it easier to carry.
A mobile media player is able to play audio and video content. The format of the audio content may be, for example, MP3, ACC or WAV, while the format of video content may be MPEG, AVI or MOV. The functionality of mobile media players may be extended by installing application programs, which are also denoted as “Apps”.
The resources of mobile computer devices may be more limited than that of desktop computers or laptops. In particular, the processor performance may be reduced to save battery energy and to provide sufficient battery operating time. For cost reduction purposes, mobile computer devices are usually equipped with less memory than desktop or laptop computers.
Often, mobile computer devices comprise hardware components, which typical mobile telephones do not comprise. For example, mobile computer devices may include a camera which can take photos and video sequences, acceleration sensors and magnetic field sensors, NFC (Near Field Communication), Bluetooth and WLAN.
As with desktop computers, the basic functionality of mobile computer devices, for example, controlling the hardware and resource scheduling, is provided by an operating system. The operating system is often adapted to the hardware to achieve an optimal utilization of the limited hardware resources. Known operating systems are “iOS”® of Apple and “Android”® of Google Inc., Mountain View, Calif., USA.
The functionality of mobile computer devices is usually extendable by downloadable computer programs. Such computer programs are also called “apps” in the context of mobile computer devices and provide, for example, travel guides, weather forecasts or games. Usually, apps are downloaded from a virtual market place on the internet. Examples of such market places are “iTunes”® of Apple and “Goolge Play”® of Google.
The present invention relates to ball games such as soccer, tennis, table tennis or golf. In the hobby or amateur field there is a need for measuring a property of a trajectory of a kicked, batted or thrown ball (e.g., a soccer, tennis or golf ball) in a simple and/or cost effective way. The property of the trajectory of the ball may for example be its speed, its acceleration when kicked, thrown or batted or its flight distance. For example hobby soccer players may want to determine which player has the “hardest” kick, e.g., who can accelerate the ball to the highest speed.
In the hobby and amateur fields, systems are known, e.g., for measuring the speed of a ball using radar. These systems are arranged along the trajectory of a ball and measure the speed based on the radiation reflected by the ball, similar to systems for speed measurements of vehicles in traffic.
In the professional field, for example, during TV transmissions of soccer games, systems are known, which optically determine the position of the players and the ball on a playing field. To this end, several stationary cameras are positioned at a certain distance from each other, such that each camera observes the playing field from a different viewing angle. The video frames captured by the cameras are analyzed by a computer with a complicated and hardware demanding software to determine the position of the players and of the ball. An example of such a professional system is the system “VIS.TRACK” of Cairos AG, Karlsbad, Germany.
The disadvantage of such systems is on the one hand that these systems must be carried to the sports venue in addition to other equipment and must be set up. On the other hand, such systems are expensive.
It is therefore the objective of the present invention to provide for a method which is suited to measure a property of a trajectory of a ball in a simple and cost effective way.